Abstract: Objective： To explore differences in incidence of gestational diabetes mellitus （ＧＤＭ） and pregnancy outcomes for patients with subclinical hypothyroidism（ＳＣＨ） ｖｅrsus normal pregnant women. Methods: A retrospective chart review of 342 pregnant women with SCＨ（ＳＣＨ ｇｒｏｕｐ） ａnd 2 605 pregnant women with normal thyroid functiｏｎ（ｃｏｎｔｒｏｌ ｇｒｏｕｐ） diagnosed by serum thyroid function screening presented for prenatal care was performed. The incidences of GDM diagnosed by oral glucose tolerance tｅｓｔ （ＯＧＴＴ） ｏｆ ｔwo groups were compared. Each group was divided into GDM & normal OGTT subgroups by results of OGTT, the following parameters of every subgroup were abstracted and appropriate statistical tests were performed: serum levels of TSH/FT4/TPOAb, incidences of abortion and premature delivery, the average weeks of delivery, the weights/lengths/head circumferences of neonates. Results: SCH group developed higher incidence of GDM than control group. Frequencies of TPOAb positivity were higher in SCH group than control group, while no significant differences were indicated between SCH subgroups neither was between control subgroups（Ｐ＜０．０１）. Serum TSH level of SCH group was higher than control group while serum FT4 level was lower（Ｐ＜０．０１）， while no significant differences of TSH and T4 levels were indicated between ＳＣＨ ｓｕｂｇｒｏｕｐｓ ｎｅｉｔｈｅｒ ｗｅｒｅ ｂｅｔｗｅｅｎ ｃｏｎｔｒｏｌ ｓｕｂｇｒｏｕｐｓ（Ｐ＞０．０５）． Ｉｎｃｉｄｅｎｃｅ ｏｆ ａｂｏｒｔｉｏｎ ａｎｄ ｐｒｅｍａｔｕｒｅ ｄｅｌｉｖｅｒｙ ｉｎ ＳＣＨ－ＧＤＭ ｓｕｂｇｒｏｕｐ ｗａｓ ｓｉｇｎｉｆｉｃａｎｔ ｈｉｇｈｅｒ ｔｈａｎ ｒａｔｅｓ ｉｎ ＳＣＨ－ｎｏｒｍａｌ ＯＧＴＴ ｓｕｂｇｒｏｕｐｓ ａｎｄ ｂｏｔｈ ｃｏｎｔｒｏｌ ｓｕｂｇｒｏｕｐｓ（Ｐ＜０．０１）． Ｔｈｅ ｒａｔｅ ｗａｓ ｈｉｇｈｅｒ ｉｎ ＳＣＨ－ｎｏｒｍａｌ ＯＧＴＴ ｓｕｂｇｒｏｕｐ ｔｈａｎ ｉｎ ｃｏｎｔｒｏｌ－ｎｏｒｍａｌ ＯＧＴＴ ｓｕｂｇｒｏｕｐ （Ｐ＜０．０１） ａｓ ｗｅｌｌ ａｓ ｉｎ ｃｏｎｔｒｏｌ－ＧＤＭ ｓｕｂｇｒｏｕｐ ｔｈａｎ ｃｏｎｔｒｏｌ－ｎｏｒｍａｌ ＯＧＴＴ ｓｕｂｇｒｏｕｐ （Ｐ＜０．０５）， ｗｈｉｌｅ ｎｏ ｓｉｇｎｉｆｉｃａｎｃｅ ｄｉｆｆｅｒｅｎｃｅ ｗａｓ ｓｈｏｗｅｄ ｂｅｔｗｅｅｎ ｓｕｂｇｒｏｕｐｓ ＳＣＨ－ｎｏｒｍａｌ ＯＧＴＴ ａｎｄ ｃｏｎｔｒｏｌ－ＧＤＭ （Ｐ＞０．０５）． Ｎｏ ｓｔａｔｉｓｔｉｃａｌ ｄｉｆｆｅｒｅｎｃｅ ｏｆ ｔｈｅ ａｖｅｒａｇｅ ｗｅｅｋｓ ｏｆ ｄｅｌｉｖｅｒｙ ｗａｓ ｆｏｕｎｄ ｂｅｔｗｅｅｎ ＳＣＨ ｓｕｂｇｒｏｕｐｓ（Ｐ＞０．０５）， ｗｈｉｌｅ ｂｏｔｈ ｗｅｒｅ ｓｈｏｒｔｅｒ ｔｈａｎ ｗｅｅｋｓ ｏｆ ｃｏｎｔｒｏｌ ｓｕｂｇｒｏｕｐｓ（Ｐ＜０．０１）. No differences were indicated in the weights/lengths/ head circumferences of neonates. Conclusions: SCH increases incidence of GDM in gestation period, Risk of adverse pregnant outcomes is higher when SCH complicated with GDM because it′s more harmful than simple disease. SCH patients should be observed emphatically, specially in monitoring and controlling levels of blood sugar.

Key words: Hypothyroidism, Diabetes, gestational, Incidence, Pregnancy outcome